It is okay to sell at any time convenient for the owner especially if they are selling for the right reason such as this which has to do with buying a house of our own it's another form of investment altogether with shelter. There are good opportunities that might never come out way twice, and when we have a means to seize it we should do so. At whatever price we sell our bitcoin holdings there shouldn't be any regrets if it served the right purpose because most definitely there's large room for another accumulation journey again.
Not just for the right reason only but at the right time, just like the OP said, he's held for years then decided to sell some portions, if he's held for a full circle, decade and beyond then he's right to take some portions to purchase that beautiful house which is a very good reason. Some folks don't really know when to sale, they sale whenever they make profits even though they've not held long enough. 2, 3 years, infact anything below a full circle is not long-term and those in that category shouldn't consider selling. Anyways I must applaud the OP for making such a good choice he saw an opportunity that was worth taking and seized it, that alone should encourage people who would come across this thread to keep holding so they'll enjoy the future benefits of doing so.